The invention relates to a transport, driving or pressing belt, in particular for belt grinding machines, comprising at least one belt material having a lower and an upper face limited by two longitudinal edges and two transverse edges extending obliquely with respect to the main extension direction of the belt, the belt material being closed and the longitudinal edges being folded down, and a method for manufacturing a transport, driving or pressing belt.
For grinding material surfaces, belt grinding machines require abrasive belts which are guided over rollers and are simultaneously driven by the rollers so that the abrasive belts move continuously. The abrasive belts are here embodied as endless or continuous abrasive belts, that means the ends are connected to each other by suited measures.
In use, the abrasive belts are pressed against the surface of the workpiece, which may be accomplished, for example, by compressed air or mechanical pressing devices. Here, the pressing device usually has a pressing belt guided over rollers which is employed in a mechanical pressing device. Such a pressing device with a pressing belt is known, for example, from German patent application 10 2014 013 741 A1.
The employed pressing belts are normally made of a woven textile of natural or plastic fibres, the two transverse edges of a finite woven textile web being connected to each other. A first possibility is to arrange the transverse edges in an overlapping manner and to connect them, preferably glue them or use a bonding sheet which is to connect the two transverse edges to each other. Due to the bonding sheet, a belt thickening results which may cause problems in individual cases.
Alternative possibilities of fastening the two transverse edges to produce a continuous belt, for example rivet fastening, is not possible in this case since irregularities of the pressing belt are transferred via the abrasive belt to the surface of the workpiece due to an increased grinding or polishing pressure on the workpiece. Here, the belts may be used as pressing belt, but also as transport or driving belt, if a sufficient useful life of the belts is ensured.
In the course of the application of the transport, driving or pressing belts it turned out that the longitudinal edges are far more stressed than the other region of the belts. The reason for this is that a deflection is effected by the rollers and the belts may additionally be subjected to torsion. If such a belt is used as intended, apart from the longitudinal edges, the connecting region between the two interconnected transverse belts is also stressed above average, thus limiting the useful life of such a belt. Normally, the woven textile of which the belt consists ravels at the longitudinal edges, and in the region of the connection of the two transverse edges, the connection is released, which may finally lead to a tearing of the belt. The edges of the transverse edges thus form the weakest point of the connection of the belts because it has the lowest resistance against the acting peeling forces, and simultaneously, the highest peeling forces occur there in case of a torsion of the belt. Thus, the two longitudinal edges and the connecting region of the two transverse edges are to be considered as critical points which may lead to a structural integrity in use.
The indicated problems also occur in transport or driving belts, leading to the same disadvantages.
From British patent specification GB 957 731 A, a continuous belt is known which is put together in abutting relationship and folded down at the longitudinal edges, whereby the folded down side edges are only connected with the top or bottom side of the driving belt. Such driving belts, however, tend to tear at the joint of the transverse edges and thus also only have a limited service life.
From British patent specification GB 851 999 A, too, a continuous belt is known which is put together without overlap and provided with a loop which connects the ends and which is connected to the top and bottom sides of the continuous belt. Especially in this embodiment, belt thickenings may occur which are undesired in many cases.